Torsional vibration is related to the degree of the influence of an excitation force frequency on a natural frequency in a transmission system, which reflects a danger degree of the resonance in the system. The torsional vibration is extremely destructive, because it may change the torsional stress acting on the shaft, increase the fatigue damage of the shaft, reduce the service life, and even cause damage or breakage to the shafting, which affects the safe and reliable operation of the shafting.
When studying the torsional vibration problem of the rotating shaft system, it is found that if the excitation force acting on the shaft is periodic, for example, in diesel engines and pumps, it will inevitably cause torsional vibration of the shafting. The existence of torsional vibration is a potential threat to the safe operation of the shafting, so it is necessary to control such torsional vibration. Taking a diesel engine as an example, the spectrum of the excitation force of such a reciprocating machine is a multi-line spectrum. Taking four-stroke as an example, the spectrum of the excitation force includes multiples of the half-harmonic of the rotation speed, thereby causing the torsional vibration at these frequencies. If the amplitude value of such torsional vibration can be controlled, the safe operation of the shafting can be greatly enhanced.
In the conventional technology, most of the torsional vibration reducers are vibration dampers. That is, the torsional vibration energy is converted into thermal energy to suppress the amplitude of the torsional vibration. Such torsional vibration reducer is complicated in structure and is expensive. Also, such torsional vibration reducer causes heating of the shafting in the energy conversion process, thereby affecting the service life of the device.
It has been studied that high amplitude values of the torsional vibration of the shafting mainly occur at points of multiples of the frequency or half-frequency of the rotation. Therefore, if it is aimed to absorb energy at these frequencies, the amplitude value of the torsional vibration can be reduced from the source, so as to ensure the safe operation of the shafting.